Warm-Season Vegetable

When to Plant Tomatoes in Wyoming

America's favorite garden vegetable (technically a fruit). Nothing beats a sun-warmed tomato straight off the vine.

The Short Answer

In Wyoming, tomatoes planting dates vary by region. In Eastern Wyoming, your average last frost is around May 10 - May 30, while Southern Wyoming sees its last frost around May 15 - Jun 1. Since tomatoes are frost-sensitive, start seeds indoors 6 weeks before your last frost, then transplant outside 2 weeks after frost danger has passed. Alkaline, thin soils. Dry climate means little organic matter naturally. Wind erosion a significant challenge. Heavy...

Wyoming Frost Dates

Your planting dates depend on which part of Wyoming you're in. Here are the frost date ranges by region:

Region Zones Last Frost (Spring) First Frost (Fall)
Eastern Wyoming 4a, 4b, 5a May 10 - May 30 Sep 10 - Sep 25
Western Wyoming 3a, 3b, 4a May 25 - Jun 15 Aug 25 - Sep 15
Southern Wyoming 4b, 5a, 5b May 15 - Jun 1 Sep 5 - Sep 20

Tomatoes Planting Schedule for Wyoming

Eastern Wyoming (Zones 4a, 4b, 5a)

Average last frost: May 10 - May 30 · Average first frost: Sep 10 - Sep 25

Start Seeds Indoors
6 wks before frost
Transplant Outside
2 wks after frost
Direct Sow
2 wks after frost

Western Wyoming (Zones 3a, 3b, 4a)

Average last frost: May 25 - Jun 15 · Average first frost: Aug 25 - Sep 15

Start Seeds Indoors
6 wks before frost
Transplant Outside
2 wks after frost
Direct Sow
2 wks after frost

Southern Wyoming (Zones 4b, 5a, 5b)

Average last frost: May 15 - Jun 1 · Average first frost: Sep 5 - Sep 20

Start Seeds Indoors
6 wks before frost
Transplant Outside
2 wks after frost
Direct Sow
2 wks after frost

Growing Tomatoes in Wyoming

Tomatoes in Wyoming's Climate

In cold climates with 120-160 frost-free days, tomatoes demand an aggressive indoor start 6-8 weeks before your last frost. Choose short-season varieties that mature in 55-65 days — Stupice, Sub Arctic Plenty, and Glacier are bred for regions exactly like yours. Black plastic mulch can raise soil temperature by 10-15°F, and floating row cover over transplants during cool June nights adds critical warmth. Your goal is getting ripe tomatoes before September frost — every warm day counts.

Soil Considerations for Wyoming

Alkaline, thin soils. Dry climate means little organic matter naturally. Wind erosion a significant challenge. Heavy amendment needed. Make sure soil has warmed to at least 60°F before planting tomatoes outside.

Wyoming Climate & Growing Season

Short growing season. Very windy — wind protection essential for gardens. Low humidity. Cool nights even in summer at elevation. Tomatoes cannot tolerate any frost, so wait until all frost danger has passed before transplanting outside. Watch local forecasts carefully in spring.

Growing season length varies across Wyoming: Eastern Wyoming (4a, 4b, 5a) has a last frost around May 10 - May 30, while Southern Wyoming (4b, 5a, 5b) sees frost end around May 15 - Jun 1. This difference matters for tomatoes — transplant timing shifts by several weeks across the state.

Growing Tips

Pinch off suckers for indeterminate varieties. Stake or cage for best results. Water at the base, not overhead, to prevent blight.

Companion Planting

Plant tomatoes alongside these companions for better growth:

Basil Carrots Peppers Marigolds

Keep tomatoes away from:

Brassicas Fennel Dill

The Bottom Line

Tomatoes can be grown successfully across Wyoming, but your exact planting dates depend on which region you're in. Eastern Wyoming gardeners should plan around a May 10 - May 30 last frost, while those in Southern Wyoming can typically plant later. For exact dates based on your zip code, use our free planting date finder.

Related Guides

Tomatoes Growing Guide National planting guide with all states Wyoming Planting Calendar All plants for Wyoming Tomatoes in Alabama Alabama planting dates Tomatoes in Alaska Alaska planting dates Tomatoes in Arizona Arizona planting dates Tomatoes in Arkansas Arkansas planting dates
Note: All dates are based on NOAA 30-year Climate Normals and represent historical averages, not predictions for any specific year. Always check your local weather forecast before planting frost-sensitive crops. Learn about our data sources.

Last reviewed: March 29, 2026

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